1. Field of the Invention
The present invention is directed to a device and a method for controlling a hybrid engine system having an internal combustion engine and a second drive unit.
2. Description of Related Art
Methods and devices for controlling an internal combustion engine in which a first drive unit in the form of an internal combustion engine and a second drive unit propel a vehicle are known from the related art. Such vehicles are customarily described as hybrid vehicles.
In order not to exceed current emission limit values, the measuring precision of the injection system of the internal combustion engine is subjected to stringent requirements over the entire life of the vehicle. Due to production spread of injectors, nozzle wear and nozzle plugging, these objectives are not able to be achieved without complex compensation strategies.
This requires the ascertainment of learned values in specific operating states such as overrun mode, the learned values being used for correcting various setpoint values. Such a correction is, for example, defined as a zero quantity calibration. This zero quantity calibration is used to ensure that the correct preinjection quantity is present over the life of the vehicle. This zero quantity calibration ascertains a minimum activating duration of the injectors, at which a predefined implementation of the injected fuel quantity by the engine occurs. This is detected in overrun mode when a defined rotational speed threshold is exceeded. Such a method is known, for example, from published German patent document DE 43 12 586.
It is problematic in this case that the internal combustion engine must usually be in the so-called overrun mode when the learned values are ascertained. In addition to overrun mode, additional boundary conditions must normally be present to be able to successfully ascertain the learned values. These additional boundary conditions include in particular an engine at operating temperature, a limited rotational speed range including a limited dynamic speed range and built up rail pressure.
Due to these problems, it is not ensured that the learned values will be learned until after a long travel distance, for example 3000 km. Therefore, the correct preinjection quantity is not metered until after this travel distance.